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Can someone please tell me a reliable way to get the last modification time of a Java resource? The resource can be a file or an entry in a JAR.
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The lastModified() method of the File class returns the last modified time of the file/directory represented by the current File object. You can get the last modified time of a particular file using this method.
Using getlastmod() Function: The getlastmod() function is used to get the last modification time of the current page.
The File. lastModified read-only property provides the last modified date of the file as the number of milliseconds since the Unix epoch (January 1, 1970 at midnight). Files without a known last modified date return the current date.
Using the stat command, we can also control the output by the -c FORMAT option. There are two formats to display the mtime: %y – displays time of last data modification in a human-readable format. %Y – displays time of last data modification in number of seconds since Epoch.
If you with "resource" mean something reachable through Class#getResource or ClassLoader#getResource, you can get the last modified time stamp through the URLConnection:
URL url = Test.class.getResource("/org/jdom/Attribute.class");
System.out.println(new Date(url.openConnection().getLastModified()));
Be aware that getLastModified() returns 0 if last modified is unknown, which unfortunately is impossible to distinguish from a real timestamp reading "January 1st, 1970, 0:00 UTC".
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The problem with url.openConnection().getLastModified() is that getLastModified() on a FileURLConnection creates an InputStream to that file. So you have to call urlConnection.getInputStream().close() after getting last modified date. In contrast JarURLConnection creates the input stream when calling getInputStream().
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